1. Field of the Invention
The present invention relates to an inflator for an inflatable air bag, and more particularly, to an inflator that is operative to fill such an air bag with a pure inert cold gas.
2. Description of the Related Art
An inflatable air bag is a safety device for protecting automotive vehicle occupants in a collision. When the vehicle strikes or is struck by a harm producing object, a sensor detects the change in motion and fires a detonator. This releases gas under high pressure from an inflator into a folded inflatable air bag. The air bag expands and provides a protective cushion that restrains the driver or passenger against various impact conditions.
Many types of inflators have been disclosed in the art for inflating an air bag for use in an inflatable restraint system. One involves the utilization of a quantity of stored compressed inert gas which is selectively released at the stored temperature to inflate the air bag. Another derives a gas source from a combustible gas generating material which, upon ignition, generates a quantity of hot gas sufficient to inflate the air bag. In a third type, the air bag inflating gas results from a combination of stored compressed inert gas and a gas generating material. The last mentioned type, commonly referred to as an augmented gas or hybrid inflator, delivers hot gas to the air bag.
As disclosed in U.S. Pat. No. 3,756,621 granted to Donald J. Lewis, et al. on Sep. 4, 1973, the use of a stored quantity of compressed argon, an inert gas, is advantageous. Compressed air and compressed nitrogen have specific problems related to their use. Air is not inert and when compressed to relatively high pressure becomes a source of significant hazard. Nitrogen is relatively inert when compressed but contributes to the production of nitrogen oxide especially when intermixed with hot gases generated from combustion.
The inflator may comprise a quantity of high pressure inert gas in a storage cylinder or bottle. An advantage accrues, however, where a stored compressed gas augmented by a generated gas is utilized. This advantage involves the addition of energy to the stored compressed gas to aid in filling of the air bag. Current technology with hybrid inflators to obtain this advantage is to heat the stored high pressure gas with some type of pyrotechnic. Such hybrid inflators, however, are subject to a disadvantage, even when argon is used as the stored compressed gas, because the gas delivered to inflate the air bag is hot and is intermixed with a gas produced by combustion of the pyrotechnic. All systems to date fill air bags with some type of gases, particulates or smoke that can be irritating or noxious.
Thus, there is a need and a demand for improvement in inflators to the end of overcoming the foregoing disadvantages. The present invention was devised to fill the gap that has existed in the art in these respects.